A REVIEW OF CHROMOSOMAL VARIATION IN DUGESIA-JAPONICA AND D-RYUKYUENSIS IN THE FAR-EAST

The chromosome numbers of Dugesia japonica Ichikawa et Kawakatsu, 1964 , are n = 8, 2x = 16 and 3x = 24; those of Dugesia ryukyuensis Kawakat su, 1976, are n = 7, 2x = 14 and 3x = 21. The karyotypes of both speci es include diploid, triploid and mixoploid; aneuploidic and mixoaneupl oidic karyotypes may occur. In 785 specimens studied of D. japonica, t he occurrence rates of specimens having each karyotype are substantial ly the same (29-37%). Diploid sexual specimens represented nearly 10% of the total and virtually no triploid or mixoploid sexual specimens w ere found. The diploid karyotype can be inherited by both sexual and a sexual reproduction; the tripioid and mixoploid karyotypes will be inh erited only by asexual reproduction. In 51 specimens studied of D. ryu kyuensis, the different karyotypes are: diploid (ca 39%), triploid (ca 57%) and mixoploid (ca 4%). Diploid sexual specimens represented near ly 25% of the total; sexual specimens with triploidic karyotypes made up nearly 27%. The diploid, triploid and mixoploid karyotypes were als o found in juveniles hatched from cocoons. The diploid karyotype is in herited by both sexual and asexual reproductions; the other karyotypes may be inherited by parthenogenesis or self-fertilization (including pseudogamy) and asexual reproduction.